1. Field of the Invention
This invention relates to the fields of magnetic recording and tribology. More specifically, this invention relates to the design of magnetic recording heads and sliders used in contact and near-contact recording systems and for the reduction of static charges that cause the accumulation of debris on the head and slider mechanisms.
2. Background of the Invention
Researchers working in the magnetic recording industry have recently begun focusing their effort on developing thin film heads having so-called integrated head/flexure/conductor structure for reading and writing of information to a disk medium. For example, such a magnetic head structure is disclosed in U.S. Pat. No. 5,041,932. In this type of recording technology, a magnetic pole element is embedded within the body of the magnetic recording head. Advanced performance is achieved in these types of magnetic recording heads by including a contact pad region which is in non-catastrophic, continuous sliding contact with the surface of the recording medium. The contact pad includes a working surface portion which is extremely small--on the order of about 20.times.30 .mu.m. The working surface portion of the contact pad actually touches the disk during normal operation.
One of the problems associated with recording heads which are in contact with the recording medium is that a substantial amount of debris is generated by the sliding action of the head against the surface of the disk. As well as being a direct result of slider-disk micro-interactions, dust and dirt from both the environment and the drive can also accumulate on and around the contact pad region. Eventually, this particulate matter finds its way into the interface between the contact pad and the disk, leading to adverse effects such as signal modulation caused by particle induced fluctuations in the head-disk spacing, and increased wear resulting from debris entering the friction zone and scratching the working surfaces.
The problem with debris accumulation is also present in more conventional slider designs in which the head flies above the surface of the disk. By way of example, in a typical magnetic recording system, the rotation of the rigid disk causes the magnetic head or slider to become aerodynamically lifted above the surface of the recording medium. This aerodynamic lifting phenomena results from the flow of air produced by the rotating magnetic disk; it is this air flow which causes the head to "fly" above the disk surface with the magnetic transducer in near-contact with the recording medium. Of course, when the rotation of the magnetic disk slows or stops, the head element is deprived of its buoyancy and it lands on the surface of the disk. Repeated starting or stopping of the disk causes the recording head to be dragged across the surface of the disk over and over again during the "take-off" and the "landing" phases of its flight.
The current trend in the industry is toward increasing the magnetic signal by lowering the slider flying height. In the conventional type of magnetic recording head described above, this means that the separation between the head and the disk is radically reduced. For instance, very low flying heights on the order of 1 to 3 microinches are becoming increasingly common. Obviously, reducing the separation between the head and the disk medium results in increased abrasive wear. Thus, in both the near-contact (flying low, e.g., at 1 to 3 microinches) and the in-contact types of recording systems, debris accumulation is a significant problem.
It should be understood that in the conventional type of magnetic recording head which flies above the surface of the disk, the working surface which touches the disk normally comprises two or more rails having flat bottom surfaces. For example, sliders of this type are disclosed in U.S. Pat. Nos. 4,870,619; 4,961,121; 4,926,274; and 4,709,284. To increase the aerodynamic lifting force, many sliders have a front taper as described in U.S. Pat. No. 4,939,603. Other designs include a sloping working surface. In either case, the taper and/or slope are in a direction that is away from the disk surface. Other prior art designs include the so-called slider camber and crown--characterized by slopes that are away from the disk surface in the direction of relative disk to slider travel direction and also in the radial direction (at right angles to slider relative travel direction). This latter type of design is usually selected based on considerations of smaller contact area so as to reduce the problem of stiction. The drawbacks to these designs however include the requirement for a higher take off velocity and an increased wear rate.
A serious problem for all prior art magnetic recording systems is the accumulation of debris on the head and slider mechanisms due to two main causes:
1) use of a liquid lubricant on the recording surface acts as a "sticky" substance that accumulates large agglomerates that get transferred to the recorder head; and PA1 2) electrostatic charge build-up on the head and slider due to triboelectric affects also accumulates debris.
The former problem has been addressed recently by N. Gitis and V. Dunn in a patent application entitled "Magnetic Head Slider with Resistance to Debris Accumulation," filed Dec. 14, 1992, Ser. No. 07/992,270, and N. Gitis in a patent application entitled, "Slider for Magnetic Recording Head Having Self-Lubricating Overcoat," filed Oct. 6, 1992, Ser. No. 07/957,423.
The latter problem has not been effectively addressed and is the subject of the current invention.